both have have pro and cons, There are certain things that realflow can do and maya can't. There's no one perfect software that can do everything. Realflow can do wet maps, meaning to simulate a water stain on the wall. Maya's ocean is easier to deal with than with realwave. There are times you need both or more softwares to finish a job. Even Studios rely on more than one software to work on a movie, also do not forget Houdini and Naiad Fluids.